1. Field of the Invention
The present invention relates to a webbing for restraining a vehicle occupant which is used in a seat belt device of a vehicle.
2. Related Art
In a three-point seat belt device, while a webbing which is inserted through a shoulder anchor is pulled out from a take-up device, a tongue plate, through which a portion of the webbing is inserted, is engaged with a buckle which is fixed to the vehicle body or to a seat. In this way, the webbing forms a lap webbing portion, which contacts the lap portion of the vehicle occupant, and a shoulder webbing portion, which contacts the vehicle occupant from the chest to the shoulder.
At ordinary times, the webbing can be pulled out from the take-up device. However, when the vehicle suddenly decelerates, pulling-out of the webbing from the take-up device is prevented, the vehicle occupant is restrained so as to not move inertially toward the front of the vehicle, and the vehicle occupant can be protected.
It is preferable to provide a means, such as that described hereinafter, so that the vehicle occupant is not subject to excessive pressure at this time.
A portion of the webbing is folded over along the transverse direction thereof and is sewn together so as to form a loop. When the vehicle occupant is restrained, when the tensile force applied to the webbing increases and reaches a predetermined value, the stitching comes undone. In this way, the length of the webbing can be increased by the length by which the loop becomes linear. Inertial movement of the vehicle occupant by an amount, which corresponds to the amount by which the length of the webbing is increased, is allowed, so that the pressure applied to the vehicle occupant is suppressed. When the loop becomes linear, from then on, inertial movement of the vehicle occupant is restricted.
However, immediately after the stitching of the webbing comes undone, the load applied between the vehicle occupant and the webbing is reduced.
When the load suddenly drops to zero or to a low load which is near zero, vibrations are generated in the webbing, which results in deterioration of the pressure suppressing function thereof.
Accordingly, it is necessary to suppress a sudden reduction in load.